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Abstract:

A medical fluid infusion system including: a fluid pathway for
transporting a pulsatile flow of fluid; a dampening element in
communication with the fluid pathway, the dampening element configured to
actively dampen pressure fluctuations of the pulsatile flow to smoothen
the pulsatile fluid flow, the dampening element operable in any
orientation; and a fluid flow sensor disposed along the fluid pathway
downstream of the dampening element to measure the flow rate of the
smoothened fluid flow.

Claims:

1. A medical fluid infusion system comprising: a fluid pathway for
transporting a pulsatile flow of fluid; a dampening element in
communication with the fluid pathway, the dampening element configured to
actively dampen pressure fluctuations of the pulsatile flow to smoothen
the pulsatile fluid flow, the dampening element operable in any
orientation; and a fluid flow sensor disposed along the fluid pathway
downstream of the dampening element to measure the flowrate of the
smoothened fluid flow.

2. The infusion system of claim 1, which includes a pulsatile infusion
pump in communication with the fluid pathway, the infusion pump causing
the pulsatile fluid flow.

3. The infusion system of claim 2, which includes a control member
operable with the fluid flow sensor and the infusion pump, the control
member configured to receive flowrate information from the flow sensor
and to adjust the infusion pump based on the flowrate information.

4. The infusion system of claim 1, wherein the dampening element includes
an outer chamber holding air compressed from a compressed air source and
an inner chamber holding the pumped fluid.

5. The infusion system of claim 1, wherein the dampening element includes
an outer chamber holding a rheologiz fluid and an inner chamber holding
the pumped fluid.

6. The infusion system of claim 1, wherein the dampening element includes
a plurality of pockets formed on an inner wall of a section of tubing to
actively provide a dampening force onto the pumped fluid.

7. The infusion system of claim 1, wherein the dampening element includes
a bellows that is expanded by the pumped fluid so as to actively provide
a dampening force onto the pumped fluid.

8. The infusion system of claim 1, wherein the dampening element includes
a coiled section of tubing to actively provide a dampening force onto the
pumped fluid.

9. The infusion system of claim 1, wherein the dampening element includes
a flexible wall to actively provide a dampening force onto the pumped
fluid.

10. The infusion system of claim 1, wherein the dampening element
includes an expandable tube to actively provide a dampening force onto
the pumped fluid.

11. The infusion system of claim 1, wherein the dampening element
includes a plurality of bunched parallel tubes to actively provide a
dampening force onto the pumped fluid.

12. An infusion system comprising: a fluid pathway; an infusion pump for
pumping a non-continuous flow of fluid through the fluid pathway; a
housing enclosing an expandable membrane, an inside of the membrane
defining a chamber that is in communication with the fluid pathway, an
outside of the chamber within the housing containing a compressible gas
that absorbs pressure fluctuations of the non-continuous flowing fluid to
smoothen the non-continuous flow, the housing and the chamber operable in
any orientation; and a fluid flow sensor disposed along the fluid pathway
downstream of the housing, the fluid flow sensor configured to measure a
flowrate of the smoothened fluid flow.

13. The medical fluid infusion system of claim 12, wherein an inlet and
an outlet of the chamber are arranged at least substantially parallel to
one another so that the fluid has to change direction after entering the
chamber.

14. The medical fluid infusion system of claim 12, wherein the expandable
membrane is an expandable balloon or an expandable wall.

15. A medical fluid infusion system comprising: an infusion pump; a fluid
pathway for transporting a pulsatile flow of fluid produced by the
infusion pump; a fluid holding compartment having an inlet and an outlet
in fluid communication with the fluid pathway; at least one compressible
air balloon located inside the fluid holding compartment that tends to
dampen fluctuations of the pulsatile flow of fluid; and a flow sensor
disposed along the fluid pathway downstream from the fluid holding
compartment.

16. The medical fluid infusion system of claim 15, wherein the inlet and
outlet of the fluid holding compartment are configured to force the flow
of fluid around the at least one compressible air balloon.

17. The medical fluid infusion system of claim 15, wherein the fluid
holding compartment houses a dividing wall that separates at least two of
the compressible air balloons.

18. The medical fluid infusion system of claim 15, wherein the inlet and
outlet of the fluid holding compartment are arranged with respect to each
other such that fluid has to change direction after entering the fluid
holding compartment.

19. A medical fluid infusion system comprising: an infusion pump that
creates at least a semi-pulsatile flow of fluid; a flow sensor disposed
downstream from the infusion pump; and a tube for carrying the at least
semi-pulsatile flow of fluid from the infusion pump to the flow sensor,
the tube enclosing at least one compressible air balloon for smoothing
the flow of fluid from the pump to the flow sensor.

20. The medical fluid infusion system of claim 19, wherein a surface of
the at least one air balloon is the inner wall surface of the tube.

[0002] The present disclosure generally relates to medical fluid delivery
systems. In particular, the present disclosure relates to devices and
methods for transforming a generally pulsatile fluid flow in an infusion
system to a smoother or less pulsatile fluid flow.

[0003] Liquid medicaments and other complex medical and therapeutic fluids
are often administered to patients through infusion therapy. Typically,
infusion therapy is accomplished by employing an infusion pump to force
fluid through an infusion circuit and into a patient. In certain
situations, such as when the infusion of fluid takes place over a long
period of time with a patient that is ambulatory, it is desirable to use
a disposable infusion system.

[0004] Because disposable infusion systems are generally single-use items,
such systems typically include relatively simple and inexpensive
components. However, one of the difficulties encountered with using
relatively simple and inexpensive components is that the components are
often not compatible for use with one another. For example, the majority
of simple and inexpensive infusion pumps generate a pulsatile or
non-continuous fluid flow. Even durable and expensive pumps generate
pulsatility. This pulsatile fluid flow is dynamic and has flowrate and
pressure fluctuations that change very quickly. Further, most simple and
inexpensive fluid flow sensors do not have the temporal resolution or the
ability to sense and calculate the flowrate of a pulsatile fluid flow.
The incompatibility of these components creates an obstacle to producing
economical disposable infusion systems that have the ability to monitor
the fluid flowrate within the infusion circuit.

[0005] In many infusion therapy applications a fluid is required to be
administered to the patient at a certain fluid flowrate to be
therapeutically effective. For example, in some applications, if the
fluid is infused too slowly, the intended therapeutic effect may be
diminished or totally non-existent. In other applications, infusion of a
fluid into the body at too high a rate can create a dangerous or overdose
situation. Thus, in a number of infusion therapy applications it is
important for the user to be able to quickly and accurately determine the
rate of fluid flow through the system, so that the flowrate can be
monitored and adjusted as needed.

[0006] In those instances in which it is important for the user to be able
to determine flowrate, a disposable infusion set will often include
either an infusion pump that generates a smooth fluid flow or a flow
sensor that has the ability to monitor and calculate the flowrate of a
pulsatile or non-continuous fluid flow. One of the disadvantages of using
a smooth flow generating infusion pump or a flow sensor that can monitor
pulsatile flow is that both of those components are relatively expensive
and add appreciably to the overall cost of the disposable infusion set.
In addition to increased cost, system components that are capable of
achieving high resolution measurements often require complex circuitry,
hardware and software architecture.

SUMMARY

[0007] The present disclosure provides an infusion system that includes a
dampening element, which transforms a generally non-continuous or
pulsatile flow of fluid within the infusion system into a generally
smoother or less pulsatile fluid flow. The incorporation of a dampening
element in to an infusion system provides a variety of benefits. For
example, the transformation of a generally pulsatile fluid flow into a
smoother fluid flow allows a relatively inexpensive fluid flow sensor,
which does not have the temporal resolution to sense and calculate
flowrate of a pulsatile flow of fluid, to be used to monitor and adjust
such fluid flow. The ability to employ a relatively inexpensive flow
sensor decreases the overall cost of the infusion system appreciably.

[0008] In general, the dampening element is disposed at a location along
the fluid pathway of an infusion system and receives a fluid having a
pulsatile fluid flow from a fluid source upstream of the dampening
element. For example, in one embodiment a medical fluid infusion system
of the present disclosure includes a fluid pathway for transporting a
pulsatile flow of fluid, e.g., a drug for infusion into the patient
pumped from a pulsatile infusion pump, e.g., a membrane pump or a
peristaltic pump. A dampening element is placed in fluid communication
with the fluid pathway. The dampening element actively dampens pressure
fluctuations of the pulsatile flow to smoothen the pulsatile fluid flow.
Advantageously, the dampening element can be operated in any orientation
and is not gravity dependent. A fluid flow sensor is disposed along the
fluid pathway downstream of the dampening element to measure the flow
rate of the smoothened fluid flow. The system can provide a common
enclosure housing both the dampening element and the fluid flow sensor.

[0009] Many different configurations for the dampening element are set
forth in detail below. For example, the dampening element can include an
outer housing holding air at atmosphere or pressurized from a compressed
air source and an inner chamber holding the pumped fluid. Or, the
dampening element can include an outer housing holding a rheologiz fluid
and an inner chamber holding the pumped fluid. Alternatively, the
dampening element includes a bellows that is expanded by the pumped fluid
so as to actively provide a compressive force onto the pumped fluid.
Further alternatively, the dampening element can include a flexible wall
that actively provides a compressive force onto the pumped fluid. Yet
further alternatively, the dampening element can include an expandable
tube to actively provide a compressive force onto the pumped fluid. In
still another alternative embodiment, the dampening element includes a
plurality of bunched parallel tubes that actively provide a compressive
force onto the pumped fluid.

[0010] In particular, one infusion system includes (i) a fluid pathway;
(ii) an infusion pump for pumping a non-continuous flow of fluid through
the fluid pathway; (iii) a housing enclosing an expandable membrane, an
inside of the membrane defining a chamber that is in communication with
the fluid pathway, an outside of the chamber within the housing
containing a compressible gas that absorbs pressure fluctuations of the
non-continuous flowing fluid to smoothen the non-continuous flow, the
housing and the chamber operable in any orientation; and (iv) a fluid
flow sensor disposed along the fluid pathway downstream of the housing,
the fluid flow sensor configured to measure a flowrate of the smoothened
fluid flow.

[0011] In another embodiment, a medical fluid infusion system includes (i)
an infusion pump; (ii) a fluid pathway for transporting a pulsatile flow
of fluid produced by the infusion pump; (iii) a fluid holding compartment
having an inlet and an outlet in fluid communication with the fluid
pathway; (iv) a chamber holding a compressible gas around at least
substantially all of an outside surface of the fluid holding compartment
so as to tend to dampen fluctuations of the pulsatile flow of fluid; and
(v) a flow sensor disposed along the fluid pathway downstream from the
fluid holding compartment and the chamber. Here, the inlet and the outlet
of the fluid holding compartment can be arranged at least substantially
parallel to one another so that the fluid has to change direction after
entering the fluid holding compartment. Also, the fluid holding
compartment can include an expandable balloon.

[0012] In a further embodiment, the medical fluid infusion system includes
(i) an infusion pump; (ii) a fluid pathway for transporting a pulsatile
flow of fluid produced by the infusion pump; (iii) a fluid holding
compartment having an inlet and an outlet in fluid communication with the
fluid pathway; (iv) at least one compressible air balloon located inside
the fluid holding compartment that tends to dampen fluctuations of the
pulsatile flow of fluid; and (v) a flow sensor disposed along the fluid
pathway downstream from the fluid holding compartment. Here, the inlet
and outlet of the fluid holding compartment can be (a) configured to
force the flow of fluid around the at least one compressible air balloon;
and (b) arranged with respect to each other such that fluid has to change
direction after entering the fluid holding compartment. In one
implementation, the fluid holding compartment houses a dividing wall that
separates at least two of the compressible air balloons.

[0013] In still another embodiment, the medical fluid infusion system
includes (i) an infusion pump that creates at least a semi-pulsatile flow
of fluid; (ii) a flow sensor disposed downstream from the infusion pump;
and (iii) a tube for carrying the at least semi-pulsatile flow of fluid
from the infusion pump to the flow sensor, the tube enclosing at least
one compressible air balloon for smoothing the flow of fluid from the
pump to the flow sensor. In one implementation, the surface of the at
least one air balloon is the inner wall surface of the tube.

[0014] It is accordingly an advantage of the present disclosure to provide
flow dampening for an infusion pump system in which the orientation of
the dampening element or dampener is immaterial.

[0015] It is another advantage of the present disclosure to provide flow
dampening for an infusion pump system in which the dampening element
actively dampens pressure fluctuations of the pulsatile flow to smoothen
the pulsatile fluid flow.

[0016] Additional features and advantages are described herein, and will
be apparent from, the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

[0017]FIG. 1 is a schematic elevation view of one embodiment for placing
the various flow pulsatility dampeners in an infusion system according to
the present disclosure.

[0018]FIG. 2 is a schematic elevation view of one embodiment for placing
the various flow pulsatility dampening devices in an infusion system
having feedback according to the present disclosure.

[0019]FIG. 3 is a flow per pump cycle schematic illustration of how the
flow pulsatility dampening devices of the present disclosure absorb
positive pressure pulses and give back flow during negative pressure
pulses due to pulsalitily inherent in the output of the medical fluid
pump of the system of the present disclosure.

[0020]FIG. 4 is a schematic view illustrating one embodiment of a flow
pulsatility dampening element of the present disclosure.

[0021]FIG. 5 is a schematic view illustrating a second embodiment of a
flow pulsatility dampening element of the present disclosure.

[0022] FIGS. 6A and 6B are schematic views illustrating a third embodiment
of a flow pulsatility dampening element of the present disclosure.

[0023] FIG. 7 is a schematic view illustrating a fourth embodiment of a
flow pulsatility dampening element of the present disclosure.

[0024]FIG. 8 is a schematic view illustrating a fifth embodiment of a
flow pulsatility dampening element of the present disclosure.

[0025] FIG. 9 is a schematic view illustrating a sixth embodiment of a
flow pulsatility dampening element of the present disclosure.

[0026]FIG. 10 is a schematic view illustrating a seventh embodiment of a
flow pulsatility dampening element of the present disclosure.

[0027]FIG. 11 is a schematic view illustrating an eighth embodiment of a
flow pulsatility dampening element of the present disclosure.

[0028]FIG. 12 is a schematic view illustrating a ninth embodiment of a
flow pulsatility dampening element of the present disclosure.

[0029]FIG. 13 is a schematic view illustrating a tenth embodiment of a
flow pulsatility dampening element of the present disclosure.

[0030]FIG. 14 is a schematic view illustrating an eleventh embodiment of
a flow pulsatility dampening element of the present disclosure.

DETAILED DESCRIPTION

[0031] Referring now to the drawings and in particular to FIG. 1, an
infusion therapy system or set 10 for infusing fluids, such as
medicaments or other therapeutic fluids, into a patient is provided. The
infusion therapy system 10 in an embodiment is a disposable infusion
system that includes relatively inexpensive component parts. In the
embodiment shown, the infusion therapy system 10 includes a fluid supply
12, an infusion pump 14 and a fluid pathway 16. In general, the infusion
pump 14 pumps fluid 18 from the fluid supply 12, through the infusion
pathway 16, to an infusion device (not shown) that delivers the fluid to
a patient. The infusion device can be any number of infusion devices,
such as a catheter, implantable port, intravenous delivery device, shunt
or other mechanism that interfaces with the patient to deliver fluid.

[0032] The infusion pump 14 is a pump that generates a pulsatile fluid
flow having pressure fluctuations, such as a micro-diaphragm or a
peristaltic pump. For example, the pump can for example be a
micro-diaphragm pump provided by thinXXS Microtechnology AG, Zweibrucken,
Germany. The pump itself can be disposable. Alternatively, the fluid
carrying components of the pump are disposable. These types of pumps are
often small in size, generally lightweight and relatively inexpensive.
The pump 14 includes an inlet port 20 for receiving fluid and an outlet
port 22 for expelling fluid. The inlet port 20 of the infusion pump 14 is
connected to the distal end portion 24 of a fluid supply conduit 26, and
the proximal end portion 28 of the fluid supply conduit 26 is connected
to fluid supply 12. The connection between the fluid supply conduit 26
and the pump 14, and other connections of components described herein,
can be any suitable type of permanent or removable connection known to
those skilled in the art, such as a male-female luer type connection or
an integral connection.

[0033] The fluid supply 12 may include a flexible dispensing bag 30
containing a fluid 18 to be infused into the patient. The dispensing bag
30 in an embodiment is made from a polymeric material and includes outlet
port 32 that is connected to the proximal end portion 28 of fluid supply
conduit 26. The dispensing bag 30 supplies the fluid 18 through the fluid
supply conduit 26 to the infusion pump 14.

[0034] Infusion pathway 16 provides a fluid path from the pump 14 to an
infusion device such as a cannula or catheter (not shown). Infusion
pathway 16 can include a first fluid conduit 34 that has a proximal end
portion 36 and a distal end portion 38. Proximal end portion 36 of first
fluid conduit 34 is connected to outlet port 22 of infusion pump 14 and
receives a pulsatile flow of fluid from the infusion pump. For example,
the rollers of a race of a peristaltic pump create a generally pulsatile
flow. The back and forth motion of a membrane or diaphragm in a membrane
pump also creates non-continuous or pulsatile flow.

[0035] A pulsatility dampening device or element (referring to any of the
dampeners 80, 90, 100a/100b, 120, 130, 140, 150, 160, 170, 180 and 190
described herein) is disposed along infusion pathway 16 at a location
that is downstream of the infusion pump 14. Distal end portion 38 of
first fluid conduit 34 is connected to the dampening element. The
dampening element receives the pulsatile fluid flow and transforms it
into a smoother or more continuous fluid flow.

[0036] Referring now to FIG. 2, infusion system 110 using any of the
dampening elements 80, 90, 100a, 100b, 120, 130, 140, 150, 160, 170, 180
and 190 discussed herein includes a control unit 112, which is in
communication with the flow sensor 50 and the infusion pump 14. The
control unit 112 can be employed to create a closed-loop controlled
infusion system that optimizes the flowrate of fluid through the infusion
system. For example, a user enters a desired flowrate into the control
unit 112. The control unit 112 communicates with the infusion pump 14 to
set the pump to pump fluid at the desired flowrate. The control unit 112
receives information from the flow sensor 50 regarding the actual
flowrate through the infusion circuit, and then processes the information
to calculate the actual flowrate. The control unit 112 can include a
proportional/integral/derivative ("PID") type of control that compares
the actual flowrate to the desired flowrate and adjusts infusion pump 14
as needed until the actual flowrate is equal to the desired flow rate.

[0037] Referring now to FIG. 3, the difference dampener embodiments set
forth herein use an expandable and/or flexible material that creates
expandable or compressible areas in the infusion pathway 16 prior to flow
sensor 50. The expandable or compressible areas are responsive to
pressure fluctuations caused by the pulsatile fluid flow, which provides
a quick-acting response to the fluctuations that results in a smoother
and more continuous flow of fluid to flow sensor 50. FIG. 3 shows a
dotted line representing a desired dampened Flow (Q) produced via the
various dampening embodiment discussed herein. A pulsatile pressure cycle
is shown as having positive and negative slopes by the solid line
representing "Flow (Q) without dampener". The increasing pressure slope
of the pressure cycle, if undampened, causes the medical fluid flowrate
to increase above the dotted desired dampened flow line "Flow (Q) with
dampener". With dampening, however, the element is instead inflated to
store a fluid volume +dv.

[0038] When the positive position of the pressure spikes subsides leading
to a negative slope of the pressure pulse, such that the solid flow line
"Flow (Q) without dampener" would if not dampened fall below the dotted
desired dampened flow line "Flow (Q) with dampener", and create a
negative volume -dv. The provision of a dampener however allows its
expandable and/or flexible material to deflect, giving back stored volume
+dv and negating negative volume -dv to smoothen the up to the desired
flowrate "Flow (Q) with dampener". The pulsatile pulse cycle just
discussed is then repeated per the cyclical nature of the pulsatile flow.

[0039] Referring now to FIG. 4, one dampener of the present disclosure is
illustrated by dampener 80. Dampener 80 includes a housing 82, which can
be a disposable, e.g., plastic, housing or a non-disposable housing,
e.g., be a permanent component of system 10. Housing 82 includes or
defines a medical fluid inlet 84 and a medical fluid outlet 86, which in
turn communicate fluidly with infusion line 16 upstream of meter 50.
Inlet 84 and outlet 86 in the illustrated embodiment are parallel and
adjacent to each other such that medical fluid flow is forced to make a
180° degree turn within a flexible dampening element 88. Inlet 84
and outlet 86 are alternatively inline with respect to each other, such
that medical fluid flows into one side of dampening element 88, through
inlet 84, and out the opposing side of dampening element 88 through
outlet 86. Outlet 86 is alternatively perpendicular to or inline with
inlet 84.

[0040] Inlet 84 and outlet 86 can be made of any suitable medical grade
tubing. Inlet 84 and outlet 86 are alternatively formed integrally with
dampening element 88, which is made of a medical grade material that is
expandable and compressible, such as, medical grade thermoset elastomers,
silicone rubbers, butyl rubbers. Dampening element 88 swells upon seeing
a positive pressure spike to absorb extra volume +dv over each pulsatile
pressure pulse illustrated in FIG. 3. The compliant material of chamber
88 contracts upon the depressurization of the pulsatile pressure spike so
as to give back +dv through outlet 86 to make up for the lack of volume
-dv caused by negative going portion of the pressure wave shown in FIG.
3.

[0041] Referring now to FIG. 5, alternative dampener 90 is illustrated.
Dampener 90 is similar in many repeats to dampener 80 and includes an
outer disposable or permanent housing 92, an inlet 94 and an outlet 86
which in turn communicate fluidly with infusion line 16 upstream of meter
50. Any alternative embodiments discussed above for housing 82, inlet 84
and outlet 86 are applicable to housing 92, inlet 94 and outlet 96. For
example, dampener 90, like dampener 80 orients inlet outlet 96 in a
direction opposite to the flow though inlet 94. In an alternative
embodiment, outlet 96 can extend perpendicular to the flow of fluid
through inlet 94 of dampener 90.

[0042] Dampener 90 replaces balloon or sack-like chamber 88 above, which
expands and compresses radially and spherically, with flexible wall 98,
which flexes away from and towards inlet 94 and outlet 96 in a bow-like
manner. Flexible wall 98 can be made of any of the materials discussed
above for dampening element 88. Upon a positive pulsatile pressure spike,
flexible wall 98 bowes or flexes to absorb the extra volume +dv. Flexible
wall 98 then un-bowes or un-flexes to a flat condition upon the
depressurization of the pulsatile pressure spike, so as to give back
positive +dv volume through outlet 96. Giving back the +dv volume through
outlet 96 makes up for the lack of volume -dv caused by the negative
portion of the pressure spike (see FIG. 3).

[0043] Referring now to FIGS. 6A and 6B alternative embodiments 100a and
100b of yet another dampener of the present disclosure are illustrated.
Dampeners 100a and 100b include housings 102a and 102b, respectively,
which can be made of any of the materials discussed herein, such as a
suitable medical grade plastic. Inlet 104 and outlet 106 for generally
vertically housing 102a and generally horizontal housing 102b are formed
in the generally parallel, opposite flow manner discussed above, and
which in turn communicate fluidly with infusion line 16 upstream of meter
50. Inlet 104 and outlet 106 can be oriented alternatively in a
perpendicular or inline manner with respect to each other.

[0044] Each housing 102a and 102b houses a highly compressible dampening
pouch or balloon 108, forming a dampening element, which is made of a
flexible e.g., plastic membrane. Pouch or balloon 108 can be filled with
air or a compressible gel. Medical fluid flows around and in contract
with balloon 108 as it travels from inlet 104 to outlet 106. In an
embodiment, balloon 108 is sized and position so as to have maximum
surface area contact with the medical fluid to optimize its dampening
effect. Balloon 108 can have a spherical, oval, elliptical or other
suitable shape. In one preferred embodiment, balloon 108 is positioned
upstream of flow sensor 50.

[0045] Upon a positive pulsatile pressure spike, balloon or pouch 108
compresses to absorb the extra volume +dv. Balloon or pouch 108 then
decompresses to its natural volume upon the depressurization of the
pulsatile pressure spike so as to give back the +dv volume through outlet
106. Giving back the +dv volume makes up for the lack of volume -dv
caused by the negative position of the pressure spike (see FIG. 3).

[0046] Referring now to FIG. 7, dampener 120 illustrates yet another
alternative dampener of the present disclosure. Dampener 120 includes a
housing 122, which can be made of any of the materials discussed herein.
Housing 122 communicates with medical fluid inlet 124 and outlet 126 in
any of the alternative ways discussed herein. Inlet 124 and outlet 126 in
turn communicate fluidly with infusion line 16 upstream of meter 50.

[0047] Housing 122 holds a plurality of compressible air bags or balloons
128, forming a dampening element. In the illustrated embodiment, balloons
128 are split on each side of divider wall 129. Alternatively, divider
wall 129 is not provided. As with balloon or pouch 108, balloons or
pouches 128 can be filled with air or a compressible gel. Balloons 129
individually and collectively dampen pulsatile medical fluid flow along
the outside surfaces of the balloons in a manner consistent with balloon
or pouch 108 of dampeners 100a and 100b of FIGS. 6A and 6B, collectively.

[0048] Referring now to FIG. 8, dampener 130 illustrates another
alternative dampening embodiment of the present disclosure. The analogous
housing of dampener 130 is a section of tubing 132 having an inlet and
134 and an outlet end 136. Tubing 132 can be formed integrally with
infusion pathway 16, be welded into infusion pathway 16, or be connected
to the infusion pathway via connectors, such as union connectors upstream
of meter 50.

[0049] Tubing 132 holds dampening pouches or balloons 138, forming a
dampening element, which operate as described above to dampen pulsatile
pressure spikes by compressing and decompressing as medical fluid flows
in a pulsatile manner around the balloons. Pouches or balloons 138 can be
formed separate from tube 132 or be formed as part of the tube. In the
latter instance, for example, balloons 138 can be formed as blister pack
or bubble wrap type structures on the inner wall of tube 132.

[0050] Referring now to FIG. 9, dampener 140 illustrates yet another
alternative pulsatile dampening structure of the present disclosure.
Dampener 140 includes a coiled section of infusion line 16, forming a
dampening element, which like dampener 130, can be formed integrally
with, be spliced into (e.g., welded, heat sealed or ultrasonically
sealed) or be connected into infusion line 16 upstream of meter 50. The
tubing of coil dampener 140 can be a thin walled compliant plastic, such
as silicone. Dampener 140 can rely on one or both of the following to
dampen pulsatile flow: (i) the twisting and untwisting of the coils of
dampener 140 in response to the positive and negative going slopes of the
pressure pulses and (ii) the material of coil 140 being highly compliant
such that the wall of the coiled tubing swells and contracts in response
to the positive and negative going slopes of the pressure pulses,
respectively.

[0051] Referring now to FIG. 10, dampener 150 illustrates yet a further
alternative pulsatile flow dampening embodiment of the present
disclosure. Dampener 150 includes a balloon housing 152, which expands
and contracts in response to the positive and negative going slopes of a
pulsatile pressure spike, as indicated by the arrowed line. Housing 152
communicates fluidly with inlet 154 and outlet 156, which in turn
communicate fluidly with infusion line 16. Inlet 154 and outlet 156 have
a 180° degree relationship, as shown, but alternatively have a
right-angled or flow through relationship.

[0052] Balloons housing includes a plurality of accordion like pleats or
walls 158, which can be made of a thin, compliant material, such as any
of the materials set forth herein. Walls or pleats 158 expand outward
upon seeing the positive slope of the pressure spike and retract upon
seeing the negative slope of the spike. The result is a smoothened and
dampened medical fluid flow over the entire pressure spike.

[0053] Referring now FIG. 11, a flow-through dampener 160 is illustrated.
Flow-through dampener includes a flexible chamber 162 that communicates
at one end with inlet 164 and a second end with outlet 166, which are
formed with, spliced into or connected into infusion line 16. The wall or
walls 168 of chamber 162 are made of any of the complaint, medically
acceptable materials described herein. Walls 168 expand or flex outward
upon seeing the positive slope of the pressure spike and contract upon
seeing the negative slope of the pressure spike to provide a smoothened,
dampened flow over the entire spike.

[0055] Referring now to FIG. 13, dampener 180 illustrates yet a further
alternative pulsatile flow dampening embodiment of the present
disclosure. Dampener 180 shown in cross-section includes a larger tube
(e.g., one to 1.5 inches outside diameter) 182, which can be of any of
the materials discussed herein, or be a rigid material that houses a
plurality of small diameter tubes 184 (e.g., 0.125 inch diameter), which
are of a compliant material, e.g., silicone, in one preferred embodiment.
The multiple tubes 184 provide an increased amount of compliant surface
area to absorb the pressure spikes. The smaller tubes 184 may also
provide an overall restricted flow that also tends to dampen the spike.

[0056] Referring now to FIG. 14, dampener 190 illustrates yet a further
alternative embodiment. Dampener 190 includes a housing 192 that
sealingly holds a chamber 198 that communicates with an inlet 194 and an
outlet 196 in any of the alternative manners described herein. Inlet 194
and an outlet 196 in turn communicate with infusion pathway 16 upstream
of meter 50. Housing 192 can be of a rigid material, while chamber 198 is
made of any of the flexible expandable materials discussed herein.
Housing 192 holds a magneto-rheologiz fluid 200 that surrounds the
outside of flexible chamber 198. The magneto-rheological fluid operates
by changing it apparent viscosity when subjected to a magnetic field.
This change in viscosity of the fluid 200 can be activated to absorb the
positive +dv volume and then the viscosity can be increased to give it
back during the negative volume -dv portion of the pressure spike.

[0057] In an alternative embodiment, magneto-rheologiz material 200 is
replaced by compressed air within a pressure holding housing 192, which
surrounds flexible chamber 198 for dampening purposes. The compressed air
can be from a cylinder, house air or via a pump of infusion pump 14.
Compressed air may be injected alternatively into air chamber 89 and/or
99 of dampeners 80 and 90 above in FIGS. 4 and 5, respectively.

[0058] If air/gas is used by any of the dampeners discussed herein (either
case in which medical fluid flows outside of or inside of a flexible air
retaining membrane) as shown in the concepts/embodiments described later,
the relationship between the stored fluid volume "dv" shown in FIG. 2,
and pressure change can be calculated using the compressed gas law called
Boyle's Law:

Po*Vo=Pf*Vf=Constant (Eq1)

in which

[0059] Po=Original pressure of uncompressed air/gas

[0060] Pf=Final pressure of compressed air/gas

[0061] Vo=Original volume of uncompressed air/gas

[0062] Vf=Final volume of compressed air/gas

[0063] Since Vf=Vo-dv by definition, substituting Vf in Eq1 yields

Po*Vo=Pf*(Vo-dv)

Po*Vo=Pf*Vo-Pf*dv

Vo=Pf*dv/(Pf-Po) or (Eq2)

dv=Vo*(Pf-Po)/Pf (Eq3)

[0064] where Eq2 and Eq3 can be used to determine the volume of air/gas
and stored fluid respectively. The total volume "dv" of air/gas needed
can be divided/distributed into a suitable number of shapes, forms, or
inserts as shown above to create a compact or easily manufactured
dampener as shown in the concepts/embodiments described later.

[0065] Aspects of the subject matter described herein may be useful alone
or in combination one or more other aspect described herein. Without
limiting the foregoing description, in a first aspect of the present
disclosure, a medical fluid infusion system includes: a fluid pathway for
transporting a pulsatile flow of fluid; a dampening element in
communication with the fluid pathway, the dampening element configured to
actively dampen pressure fluctuations of the pulsatile flow to smoothen
the pulsatile fluid flow, the dampening element operable in any
orientation; and a fluid flow sensor disposed along the fluid pathway
downstream of the dampening element to measure the flowrate of the
smoothened fluid flow.

[0066] In accordance with a second aspect of the present disclosure, which
may be used in combination with the first aspect, the infusion includes a
pulsatile infusion pump in communication with the fluid pathway, the
infusion pump causing the pulsatile fluid flow.

[0067] In accordance with a third aspect of the present disclosure, which
may be used in combination with the second aspect, the infusion includes
a control member operable with the fluid flow sensor and the infusion
pump, the control member configured to receive flowrate information from
the flow sensor and to adjust the infusion pump based on the flowrate
information.

[0068] In accordance with a fourth aspect of the present disclosure, which
may be used in combination with any one or more of the preceding aspects,
the dampening element includes an outer chamber holding air compressed
from a compressed air source and an inner chamber holding the pumped
fluid.

[0069] In accordance with a fifth aspect of the present disclosure, which
may be used in combination with any one or more of the preceding aspects,
the dampening element includes an outer chamber holding a rheologiz fluid
and an inner chamber holding the pumped fluid.

[0070] In accordance with a sixth aspect of the present disclosure, which
may be used in combination with any one or more of the preceding aspects,
the dampening element includes a plurality of pockets formed on an inner
wall of a section of tubing to actively provide a dampening force onto
the pumped fluid.

[0071] In accordance with a seventh aspect of the present disclosure,
which may be used in combination with any one or more of the preceding
aspects, the dampening element includes a bellows that is expanded by the
pumped fluid so as to actively provide a dampening force onto the pumped
fluid.

[0072] In accordance with an eighth aspect of the present disclosure,
which may be used in combination with any one or more of the preceding
aspects, the dampening element includes a coiled section of tubing to
actively provide a dampening force onto the pumped fluid.

[0073] In accordance with a ninth aspect of the present disclosure, which
may be used in combination with any one or more of the preceding aspects,
the dampening element includes a flexible wall to actively provide a
dampening force onto the pumped fluid.

[0074] In accordance with a tenth aspect of the present disclosure, which
may be used in combination with any one or more of the preceding aspects,
the dampening element includes an expandable tube to actively provide a
dampening force onto the pumped fluid.

[0075] In accordance with an eleventh aspect of the present disclosure,
which may be used in combination with any one or more of the preceding
aspects, the dampening element includes a plurality of bunched parallel
tubes to actively provide a dampening force onto the pumped fluid.

[0076] In accordance with a twelfth aspect of the present disclosure,
which may be used in combination with any one or more of the preceding
aspects, an infusion system includes: a fluid pathway; an infusion pump
for pumping a non-continuous flow of fluid through the fluid pathway; a
housing enclosing an expandable membrane, an inside of the membrane
defining a chamber that is in communication with the fluid pathway, an
outside of the chamber within the housing containing a compressible gas
that absorbs pressure fluctuations of the non-continuous flowing fluid to
smoothen the non-continuous flow, the housing and the chamber operable in
any orientation; and a fluid flow sensor disposed along the fluid pathway
downstream of the housing, the fluid flow sensor configured to measure a
flowrate of the smoothened fluid flow.

[0077] In accordance with a thirteenth aspect of the present disclosure,
which may be used with any one or more of the preceding aspects in
combination with aspect twelve, an inlet and an outlet of the chamber are
arranged at least substantially parallel to one another so that the fluid
has to change direction after entering the chamber.

[0078] In accordance with a fourteenth aspect of the present disclosure,
which may be used with any one or more of the preceding aspects in
combination with aspect twelve, the expandable membrane is an expandable
balloon or an expandable wall.

[0079] In accordance with a fifteenth aspect of the present disclosure,
which may be used in combination with any one or more of the preceding
aspects, an infusion system includes: an infusion pump; a fluid pathway
for transporting a pulsatile flow of fluid produced by the infusion pump;
a fluid holding compartment having an inlet and an outlet in fluid
communication with the fluid pathway; at least one compressible air
balloon located inside the fluid holding compartment that tends to dampen
fluctuations of the pulsatile flow of fluid; and a flow sensor disposed
along the fluid pathway downstream from the fluid holding compartment.

[0080] In accordance with a sixteenth aspect of the present disclosure,
which may be used with any one or more of the preceding aspects in
combination with aspect fifteen, the inlet and outlet of the fluid
holding compartment are configured to force the flow of fluid around the
at least one compressible air balloon.

[0081] In accordance with a seventeenth aspect of the present disclosure,
which may be used with any one or more of the preceding aspects in
combination with aspect fifteen, the fluid holding compartment houses a
dividing wall that separates at least two of the compressible air
balloons.

[0082] In accordance with an eighteenth aspect of the present disclosure,
which may be used with any one or more of the preceding aspects in
combination with aspect fifteen, the inlet and outlet of the fluid
holding compartment are arranged with respect to each other such that
fluid has to change direction after entering the fluid holding
compartment.

[0083] In accordance with a nineteenth aspect of the present disclosure,
which may be used in combination with any one or more of the preceding
aspects, an infusion system includes: a medical fluid infusion system
includes: an infusion pump that creates at least a semi-pulsatile flow of
fluid; a flow sensor disposed downstream from the infusion pump; and a
tube for carrying the at least semi-pulsatile flow of fluid from the
infusion pump to the flow sensor, the tube enclosing at least one
compressible air balloon for smoothing the flow of fluid from the pump to
the flow sensor.

[0084] In accordance with a twentieth aspect of the present disclosure,
which may be used with any one or more of the preceding aspects in
combination with aspect nineteen, a surface of the at least one air
balloon is the inner wall surface of the tube.

[0085] In accordance with a twenty-first aspect of the present disclosure,
any of the structure and functionality illustrated and described in
connection with FIG. 1 may be used in combination with any one or more of
the preceding aspects.

[0086] In accordance with a twenty-second aspect of the present
disclosure, any of the structure and functionality illustrated and
described in connection with FIG. 2 may be used in combination with any
one or more of the preceding aspects.

[0087] In accordance with a twenty-third aspect of the present disclosure,
any of the structure and functionality illustrated and described in
connection with FIG. 3 may be used in combination with any one or more of
the preceding aspects.

[0088] In accordance with a twenty-fourth aspect of the present
disclosure, any of the structure and functionality illustrated and
described in connection with FIG. 4 may be used in combination with any
one or more of the preceding aspects.

[0089] In accordance with a twenty-fifth aspect of the present disclosure,
any of the structure and functionality illustrated and described in
connection with FIG. 5 may be used in combination with any one or more of
the preceding aspects.

[0090] In accordance with a twenty-sixth aspect of the present disclosure,
any of the structure and functionality illustrated and described in
connection with FIGS. 6A and 6B may be used in combination with any one
or more of the preceding aspects.

[0091] In accordance with a twenty-seventh aspect of the present
disclosure, any of the structure and functionality illustrated and
described in connection with FIG. 7 may be used in combination with any
one or more of the preceding aspects.

[0092] In accordance with a twenty-eighth aspect of the present
disclosure, any of the structure and functionality illustrated and
described in connection with FIG. 8 may be used in combination with any
one or more of the preceding aspects.

[0093] In accordance with a twenty-ninth aspect of the present disclosure,
any of the structure and functionality illustrated and described in
connection with FIG. 9 may be used in combination with any one or more of
the preceding aspects.

[0094] In accordance with a thirtieth aspect of the present disclosure,
any of the structure and functionality illustrated and described in
connection with FIG. 10 may be used in combination with any one or more
of the preceding aspects.

[0095] In accordance with a thirty-first aspect of the present disclosure,
any of the structure and functionality illustrated and described in
connection with FIG. 11 may be used in combination with any one or more
of the preceding aspects.

[0096] In accordance with a thirty-second aspect of the present
disclosure, any of the structure and functionality illustrated and
described in connection with FIG. 12 may be used in combination with any
one or more of the preceding aspects.

[0097] In accordance with a thirty-third aspect of the present disclosure,
any of the structure and functionality illustrated and described in
connection with FIG. 13 may be used in combination with any one or more
of the preceding aspects.

[0098] In accordance with a thirty-fourth aspect of the present
disclosure, any of the structure and functionality illustrated and
described in connection with FIG. 14 may be used in combination with any
one or more of the preceding aspects.

[0099] It should be understood that various changes and modifications to
the presently preferred embodiments described herein will be apparent to
those skilled in the art. Such changes and modifications can be made
without departing from the spirit and scope of the present subject matter
and without diminishing its intended advantages. It is therefore intended
that such changes and modifications be covered by the appended claims.